The conventionally well-known methods for synthesizing carbonyl compounds by the decomposition of hydroperoxide are as follows:
(1) A method of decomposition by heating in the coexistence of an aqueous alkali solution. PA1 (2) A method of decomposition with potassium ferrocyanide [J.A.C.S., 75, 4268 (1953)]. PA1 (3) A method of decomposition with a ferrous salt (Fe.sup.++) [J. Org. Chem., 15, 763 (1950), etc.].
By the method (1), however, large quantities of alcohol compounds are produced at the same time, so that carbonyl compounds cannot be obtained in good yields.
The method (2), according to the description of the literature cited, produces acetophenone in very high yield from cumene hydroperoxide, but because of this reaction being almost stoichiometric, a large quantity of expensive potassium ferrocyanide need to be used. Consequently, this method cannot always be said to be industrially advantageous.
The method (3) is described in many studies and literatures from of old, and, for example, according to the description of the literature given above, acetophenone is obtained in a yield of 71% by the decomposition of cumene hydroperoxide with a ferrous salt (Fe.sup.++). In this method with a ferrous salt (Fe.sup.++), however, the amount of the salt used is generally large, and the yield is also low, so that this method cannot always be said to be advantageous from the industrial point of view, too.
In view of the present situation like this, the present inventors extensively studied and found that, by decomposing a hydroperoxide in an inert gas atmosphere in the presence of an aqueous layer containing an iron salt, a copper salt and an acid, aromatic carbonyl compounds can be obtained in markedly high yields as well as with a rapid decomposition rate. The present invention was completed based on this finding.